"""This module defines a checkbox widget"""
from __future__ import annotations
from typing import Callable, Optional
from asciimatics.event import KeyboardEvent, MouseEvent, Event
from asciimatics.widgets.widget import Widget


class CheckBox(Widget):
    """
    A CheckBox widget is used to ask for Boolean (i.e. yes/no) input.

    It consists of an optional label (typically used for the first in a group of CheckBoxes),
    the box and a field name.
    """

    __slots__ = ["_text", "_on_change"]

    def __init__(self,
                 text: str,
                 label: Optional[str] = None,
                 name: Optional[str] = None,
                 on_change: Optional[Callable] = None,
                 **kwargs):
        """
        :param text: The text to explain this specific field to the user.
        :param label: An optional label for the widget.
        :param name: The internal name for the widget.
        :param on_change: Optional function to call when text changes.

        Also see the common keyword arguments in :py:obj:`.Widget`.
        """
        super().__init__(name, **kwargs)
        self._text = text
        self._label = label
        self._on_change = on_change

    def update(self, frame_no: int):
        self._draw_label()

        # Render this checkbox.
        assert self._frame
        check_char = "✓" if self._frame.canvas.unicode_aware else "X"
        (colour, attr, bg) = self._pick_colours("control", self._has_focus or self._value)
        self._frame.canvas.print_at(f"[{check_char if self._value else ' '}] ",
                                    self._x + self._offset,
                                    self._y,
                                    colour,
                                    attr,
                                    bg)
        (colour, attr, bg) = self._pick_colours("field", self._has_focus or self._value)
        self._frame.canvas.print_at(self._text, self._x + self._offset + 4, self._y, colour, attr, bg)

    def reset(self):
        pass

    def process_event(self, event: Optional[Event]) -> Optional[Event]:
        if isinstance(event, KeyboardEvent):
            if event.key_code in [ord(" "), 10, 13]:
                # Use property to trigger events.
                self.value = not self._value
            else:
                # Ignore any other key press.
                return event
        elif isinstance(event, MouseEvent):
            # Mouse event - rebase coordinates to Frame context.
            if event.buttons != 0:
                if self.is_mouse_over(event, include_label=False):
                    # Use property to trigger events.
                    self.value = not self._value
                    return None
            # Ignore other mouse events.
            return event
        else:
            # Ignore other events
            return event

        # If we got here, we processed the event - swallow it.
        return None

    def required_height(self, offset: int, width: int):
        return 1

    @property
    def value(self):
        """
        The current value for this Checkbox.
        """
        return self._value

    @value.setter
    def value(self, new_value):
        # Only trigger the notification after we've changed the value.
        old_value = self._value
        self._value = new_value if new_value else False
        if old_value != self._value and self._on_change:
            self._on_change()
